UNIVERSITY OF ECONOMICS, PRAGUE Faculty of Informatics and Statistics Department of Information Technologies (KIT) Trends in web application development Bachelor's Thesis Vojtěch Jasný Thesis Supervisor: Ing. Tomáš Brabec January 2007 Abstrakt Bakalářská práce se věnuje dvěma tématům: prvním z nich jsou trendy ve vývoji webových aplikací z pohledu klienta. Jsou popsány techniky AJAX a COMET, formát pro výměnu dat JSON, nástroje použitelné pro ladění aplikací v Javascriptu a před- staveny tři Javascriptové knihovny. Důležitou součástí vývoje na klientovi jsou for- muláře, které mají v dnešní podobě daleko ideálu. Je proto obsažen popis technologií XForms a Web Forms 2.0 a jejich porovnání. Druhým tématem je vývoj aplikací na straně serveru. Nejprve jsou hodnoceny stávající najčastěji používané technologie. Dále jsou představeny čtyři frameworky, které jsou na závěr porovnávány dle sady kritérií a je diskutována jejich vhodnost pro různé druhy nasazení. Zastoupeny jsou jazyky Python, Ruby a Java. Abstract The thesis is divided between two main topics: the first are trends in web application development on the client-side. Described are AJAX and COMET techniques, JSON format for data interchange, tools usable to debug Javascript applications and three Javascript libraries. Important part of client-side development are forms, which are far from ideal in their current state. Hence description of XForms and Web Forms 2.0 and their comparison is included. The second topic is server-side development. First the most used technologies used today are evaluated. Further, several frameworks are described and compared on a set of criteria. Python, Ruby and Java languages are represented. Acknowledgments I would like to thank Christian Heilmann from Yahoo! UK Ltd., who kindly provided me with unedited chapter on Javascript libraries from his upcoming book. I would also like to thank my supervisor for his useful comments and suggestions. Declaration - Prohlášení Prohlašuji, že jsem bakalářskou práci vypracoval samostatně a použil pouze literaturu uvedenou v přiloženém seznamu. Nemám námitek proti půjčení práce se souhlasem katedry ani proti zveřejnění práce nebo její části. V Praze dne 11. května 2007 Vojtěch Jasný Table of Contents 1. Introduction ........................................................................................................................ 7 2. Client-side development .................................................................................................. 9 2.1. Browser programming .......................................................................................... 9 2.1.1. Browsers in the market ............................................................................. 10 2.1.2. AJAX & COMET ........................................................................................ 11 2.1.3. JSON ............................................................................................................ 15 2.1.4. Javascript libraries ..................................................................................... 16 2.2. Markup languages ................................................................................................ 23 2.2.1. XForms ........................................................................................................ 23 2.2.2. Web Forms 2.0 ............................................................................................ 28 2.2.3. Comparison ................................................................................................ 30 3. Server-side development ................................................................................................ 31 3.1. Presence ................................................................................................................. 31 3.1.1. Model-View-Controller pattern ............................................................... 31 3.1.2. PHP .............................................................................................................. 32 3.1.3. ASP.NET ...................................................................................................... 34 3.1.4. Java Platform, Enterprise Edition (Java EE) .......................................... 34 3.2. Trends ..................................................................................................................... 36 3.2.1. GWT - Google Web Toolkit ...................................................................... 37 3.2.2. Turbogears .................................................................................................. 38 3.2.3. Ruby on Rails ............................................................................................. 42 3.2.4. Django ......................................................................................................... 43 3.2.5. Evaluation ................................................................................................... 45 4. Conclusion ........................................................................................................................ 49 Bibliography ......................................................................................................................... 51 Glossary ................................................................................................................................ 53 6 Chapter 1 Introduction Advances in web application development are very rapid, however certain milestones however can be identified. Currently as developers, find ourselves on the verge of one such milestone - the onset of technologies and techniques sometimes imprecisely labeled as Web 2.0 is reshaping the ways web applications look and feel. Along with changes in the presentation layer, changes in the way business logic is structured and imple- mented also take place. In this bachelor's thesis I will seek to describe some of the trends that have already found their way to the world of web application development and some which are yet to be explored by the web development community too. I divide my attention equally between client and server development. Accordingly, this thesis has two main chapters: first chapter gives overview of techniques used in client-side programming and the second chapter is focused on server-side development frameworks. Client-side programming or scripting is generally defined as a group of programs run one the side of the client (which in web programming is the browser). They are usually written in Javascript, less often in VBScript and they utilise the Document Object Model (DOM) to make changes to the rendered document. When and how scripts are executed is defined in the W3C HTML standard (events and respective event attributes). Server-side programming deals with generation of markup document on the server, querying databases (or other data sources) in the process and sending the output back through the network using HTTP protocol. At the side of the client, the most notable trend in web application development is the use of asynchronous HTTP requests for XML or JSON message exchange with the web server, without the necessity of reloading the whole page for updates. This tech- nique can be implemented either from scratch or a wrapper library can be used to hide differences between browsers from the programmer and to provide more comfort during development. The first part of the client-side development chapter describes features of three such libraries - prototype, Dojo and Yahoo! User Interface. The second 7 1. Introduction part pertains to markup languages, specifically XForms and Web Forms 2.0. Forms are a critical component in web applications and their present capabilities are lackluster. In the future one of these standards is expected to replace them. In the server-side chapter I briefly comment on the pros and cons of the three technologies prevalent in server-side development today - PHP, ASP.NET and J2EE. I then proceed with introduction of four frameworks which are now gaining in popularity. First is the Google Web Toolkit (GWT), a library that introduces an interesting devel- opment model based on translating Java code to Javascript. Two dynamic languages, Python and Ruby, are also represented. From the land the snake I introduce two frameworks - Turbogears and Django. In Ruby, the prevalent framework is Ruby on Rails. Although the four are very different products, they have one thing in common - the aspiration to make building complex web publishing and content management systems as simple and fast as possible. At the end of the chapter I attempt to compare the frameworks and discuss. All of the described products are evaluated from the perspective of medium-size website development (perhaps an e-commerce site or a corporate website with complex web publishing system). Building large sites with millions of unique visitors a month poses completely different challenges both in terms technology choices and performance requirements and is beyond the scope of this thesis. 8 Chapter 2 Client-side development 2.1. Browser programming One of the troubles of client-side web programming is long delay before new techno- logies move from drafts to real world adoption. The reason for this lies in the result of the browser war during the late 90s. At that time Microsoft acquired an overwhelming majority of the web-browser market, peaking at 96%. Since then, with advent of altern- ative web-browsing programs, Microsoft is slowly losing ground to them, but even most